In Finnish mythology, Kinahmi is a great whirl in sea. Kinahmi is a way to Tuonela, the land of dead people. Souls of evil people must swim through Kinahmi to enter Tuonela. Swords, axes and needles moves with water and hurts souls of evil people.
There is also a different story about water between land of dead and land of living. In that story the water is calm, black river.